Interlocking wood grain patterns provide improved wood strength properties in forks of hazel (Corylus avellana L.)

摘要

Xylem found in the stems of woody plants has contrasting strength in different planes due to its anisotropy. At the apex of the junctions of woody plant branches, sufficient wood strength is needed to prevent the arising branches splitting apart. Themain aim of this research was to address an issue so far overlooked, which is the contribution of wood grain orientation and patterns at this location (the apex of such junctions) to supplying the required strength. In this study, the wood grain patternsof xylem produced at the apex of junctions of hazel (Corylus avellana L.) were investigated. The mechanical properties were determined using compression and tensile tests of excised wood samples with an Instron~R Universal Testing Machine. Sample strength was contrasted with the strength of xylem produced at the side of the junctions and in the adjacent lower stems. Wood formed at the top of junctions in the hazel exhibited more tortuous wood grain patterns and had twice the radial and tangential tensile strength when compared with adjacent wood formed in the stem. It also had significantly higher radial and tangential compression strength. Density of xylem at the apex of hazel junctions was 13.4% greater than in the adjacent stem. The authors conclude that tortuous wood grain patterns supply additional strength to junctions in hazel trees. This mechanical arrangement should inform anatomical studies of junctions and may inform the design of manufactured Y-shaped components made from fibrous composite materials.